package com.hackerrank.contests.july13.challenges.gameofthrones1;

import java.util.Scanner;

public class Solution {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		char ch[] = in.next().toCharArray();
		int c[] = new int[26];
		for(char h : ch)
			c[h - 'a']++;
		int n = 0;
		for(int i = 0; i < c.length; i++) {
			n += c[i] % 2;
			if(n > 1) {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
}
